Email notifications are not working. How can I fix this?

If you had logged into multiple gmail accounts in the same browser, the email triggers may not have been setup properly. Please open an incognito window, sign in with your gmail account used to install the add-on (make sure that you haven't signed in with any other gmail account) and try to use the add-on. It should work.

Error when trying to setup email notifications when signed into multiple gmail accounts
Email notifications enabled when signed in with only the gmail account used to install the add-on